205xs idle problem

macaroni · Unread post by **macaroni** » 25 Feb 2004, 03:58

Hi,
my 205xs, TU3S, won't idle smoothly unless the mixture screw is turned almost completely out. The ignition timing is set at about 10 degrees BTDC, I have just had a new ignition amplifier module fitted too.
Any ideas on what could be up?
Any help greatly appreciated.
Cheers,
Antony

red161 · Unread post by **red161** » 28 Feb 2004, 05:52

I had a similar problem on a mates Ford XR2, it just would not idle at all, we checked a few things including the timing which was correct, I traced the problem to a breather pipe attached to the inlet manifold - it had a hole in it causing the engine to suck in air on idle. The pipe was fixed and it ran and idled like a dream.

macaroni · Unread post by **macaroni** » 03 Mar 2004, 14:16

Cheers for that. I had a look at the pipe going from the inlet manifold to the air filter and it was indeed split!
I replaced it and it runs better.
However, it still runs better if I richen the mixture as far as it will go.

Unread post by **RichardW** » 03 Mar 2004, 15:02

Assume we are talking a carb here? In which case whip out the idle jet and blow it out - you'll probably find it full of crud. Where it is depends on the carb, but if it's a Solex PB type it's low down on the RHS of the carb body as you look at it - a big brass screw. If this doesn't work, then it might be sucking air through the gsket under the carb - presume this 205 is fitted with the old 'laid back' type engine?
PS also check the vacuum hose to the distributor, and the servo if fitted. 10° seems like a lot of advance, particularly if you are running it on 95 RON unleaded, but I might be wrong[:D].

macaroni · Unread post by **macaroni** » 04 Mar 2004, 13:06

Cheers for the info Richard. Mine is the TU3S engine, so not the laid back type.
I stripped the carb last night and found the filter at the fuel intake full of crap. That might explain it. Now that is sorted I do need to retime it. The recommended timing is 8 deg, but as you pointed out, it might need adjusting to run on unleaded.
Thanks again!

Unread post by **RichardW** » 04 Mar 2004, 13:54

Usually retard the timing by about 4° if the original is for 98RON and you want to run 95 RON unleaded. The TU engine *should* have hardened valve seats and be OK on unleaded (I ran my BX 14 on unleaded).

macaroni · Unread post by **macaroni** » 06 Mar 2004, 22:47

Richard,
is that retard it 4 deg from the 8 it should be, or make the timing 4 deg BTDC?
It idles rough at 8 deg as it is, it would probably stall at 4 deg!
It seems to idle better the more I retard it, but I am sure that can't be right.

Unread post by **RichardW** » 08 Mar 2004, 13:19

Retard ignition so that it is set at 4° BTDC (I am working from an 8 year old memory now!). It shouldn't make that much difference as when I fixed the dizzy on my Visa and put it back on it was running at about 5° ATDC and still ticked over OK. Assuming you have fully cleaned out the carb, the next thing you have to look for is an air leak - dizzy vac advance, brake servo / pipe, inlet manifold gasket. If you draw a blank here then you might want to physically check the camshaft timing - eg take the rocker cover off and check that the valves are opening and closing at the right time - and whilst you've got the cover off check the valve clearances.
There's lots of places to look yet!

macaroni · Unread post by **macaroni** » 07 Jul 2004, 13:04

Richard,
sorry to resurrect this, but after much work on the car, this problem still exists. The carb has been stripped and refurbished, the cam replaced with a fast road one and all the valve clearances checked and re-checked.
The car pulls very well up to 7000rpm, but still is very lumpy at idle, unless the timing is set at 10 or 12 deg BTDC. Having used it with this timing for a while without problem, could it be that is how it should be?

Unread post by **RichardW** » 07 Jul 2004, 20:32

Hi,
Something seems amiss, as 12° BTDC will give nearly 40°C at full advance - I would expect it to pink like mad and overheat at this level. Assuming you're not having these problems, and not excessive fuel consmption, I'd just leave as is. Of course a 'hot' cam is not exactly known for giving a smooth idle, and you may want to just up the revs a bit to make it tick over. I'd get the CO level checked at idle too to make sure the mixture is OK.
If all is well, and no running probs, I'd just ignore the numbers.....

macaroni · Unread post by **macaroni** » 08 Jul 2004, 00:32

Cheers.
I kind of came to that conclusion today. I had it on the recommended 8 deg and it ran like a dog, even with the idle at 1200rpm. So I have just reset it to 12 and set the idle to 1000rpm and it is sweet. It doesn't pink or get exccessively hot so I will leave it there.
Thanks for your help.